I. Field of the Invention
This invention relates generally to apparatus for allowing vehicle tires with demountable rims to be mounted on tire test equipment, such as wheel balancing equipment, and more particularly to an improved adapter having a self-centering mechanism incorporated therein and an improved clamping structure allowing the adapter to be mated with the exposed front edge surface of the demountable rim.
II. Discussion of the Prior Art
One type of wheel rim often used on large semi-trailer trucks is a so-called demountable rim, also sometimes referred to as a Dayton# rim. A cross-section of such a rim is illustrated in FIG. 1 and identified by the numeral 10. It is characterized by the fact that it does not have a central hub with bolt holes through which bolts or studs may pass for mounting the wheel to the vehicle. Instead, it is to be used with a cast spoke wheel. Because it does not include a center hub, a demountable rim wheel cannot be directly mounted on the spindle cone of a conventional dynamic wheel balancer. Thus, an adapter must be provided.
Referring to FIG. 1, there is shown a prior art adapter used for many years over which the present invention is deemed to be an improvement. It includes a tapered peripheral surface at its edge 12 which must be mated with a correspondingly tapered surface 14 formed just beneath the bead seat surface 16 of the rim 10 when inserted through the rear of the rim and pushed forward toward the front opening of the rim. The adapter 11 includes a central opening 18 which is arranged to mate with the slanting surface 20 of the spindle cone 22. The spindle cone screws onto a shaft 24 which is generally disposed in a horizontal position and which is driven at relatively high speeds during the dynamic balancing operation.
A primary problem with the prior art adapter 11 shown in FIG. 1 is the difficulty in accurately centering the adapter relative to the rim 10 which it is intended to support. Unless precise centering is accomplished, true balancing cannot be expected. The centering is made difficult because there is a range of angular tilt which is experienced as the ramp 12 on the adapter abuts the ramp 14 on the rim 10. When an operator thinks he has the adapter properly centered relative to the rim, he then assembles the clamping lug 26 on the threaded stud 28 and tightens down the hex nuts 30. This operation can also result in shifting of the rim relative to the adapter. If it is determined during the balancing test phase that the rim/adapter are not properly centered, the operator must again back off the clamping nuts 30 and attempt to precisely locate the adapter relative to the surface with which it mates on the rim. This becomes a hit-or-miss process and may take as long as 20 to 30 minutes to accomplish.